The main goal of the research has remained the development of more efficient computer methods for ECG analysis. Main efforts during the last year were directed toward development of an automated comparison program for serial electrocardiograms. Such comparisons are essential in clinical patient evaluations, in mass screening programs, and in epidemiological investigations. Two separate tasks are involved in this development. First, an efficient storage and retrieval system is needed for rapid access to old records. A disk drive was found most efficient for this purpose. The second task consists of the comparisons proper. Both ECG measurements and diagnostic statements need to be compared. To be clinically significant, they have to exceed the normal day-to-day variability which is commonly encountered in serial ECG's. Measurements and diagnostic changes which exceed this variability are provided in the computer report. Several other studies dealt with particular diagnostic problems which are commonly encountered in clinical electrocardiography. Multivariate statistical procedures were applied in order to improve differential diagnosis by computer. Examples of such problems are found in the separation between right ventricular hypertrophy and true posterior myocardial infarcts or between cases with ventricular conduction defects with infarcts and without infarcts. In all instances, multivariate analysis led to enhancement of diagnostic differentiation.